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1
Content available remote Investigation of SOFC material properties for plant-level modeling
100%
Kupecki J. , Milewski J. , Jewulski J.
Open Chemistry
|
2013
|
tom 11
|
nr 5
664-671
EN
This article describes results of a recent study of SOFC (Solid Oxide Fuel Cell) material properties using a numerical tool. The created model was validated against experimental data collected for two different solid oxide fuel cells. With focus on ionic and electronic conductivities, temperature influence was investigated. Results are presented, compared with available data, and discussed. Model of a micro-CHP (Combined Heat and Power) unit based on a SOFC stack was used for evaluation of system performance with different cells. On-site generated bio-syngas was considered as a fuel fed for the unit. The overall system efficiency was analyzed using an Aspen HYSYS modeling environment. Properties of two generic electrolyte materials were implemented in the models for evaluation of a co-generative unit operation. Electrical and overall efficiencies of systems based on those cells were compared and differences were observed. Micro-scale power units with fuel cells are a promising technology for highly efficient distributed cogeneration. As it was concluded, selection of a proper cell is crucial to assure high system efficiency. [...]
2
Content available remote Statistical interpretation of medical data of patients with alcohol abuse
100%
Bardarov V. , Simeonova P. , Neikova L. , Bardarov K. , Simeonov V. , Tsakovski S. , Kanev K.
Open Medicine
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2012
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tom 7
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nr 4
465-474
EN
An attempt is made to assess a set of biochemical, kinetic and anthropometric data for patients suffering from alcohol abuse (alcoholics) and healthy patients (non-alcoholics). The main goal is to identify the data set structure, finding groups of similarity among the clinical parameters or among the patients. Multivariate statistical methods (cluster analysis and principal components analysis) were used to assess the data collection. Several significant patterns of related parameters were found to be representative of the role of the liver function, kinetic and anthropometric indicators (conditionally named “liver function factor”, “ethanol metabolism factor”, “body weight factor”, and “acetaldehyde metabolic factor”). An effort is made to connect the role of kinetic parameters for acetaldehyde metabolism with biochemical, ethanol kinetic and anthropometric data in parallel.
3
Content available remote New Regression Models to Evaluate the Relationship between Biomechanics of Gymnastic Vault and Initial Vault Difficulty Values
100%
Atiković A.
Journal of Human Kinetics
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2012
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tom 35
|
nr 1
119-126
EN
The main objective of this paper was to determine the relationship between biomechanical parameters of vault flights with respect to new models of initial vault difficulty values in men’s artistic gymnastic. The study sample included vaults (n=64) and models (n=5) from the 2009 Code of Points (CoP) of the Federation International of Gymnastics (FIG). The dependent variable included all difficulty values ranging from 2-7.2 points, while the sample of independent variables included twelve biomechanical parameters. After implementing the regression analysis, it could be established that the best model derived only the second flight phase with 95% of explained variance.
4
Content available remote Mathematical modeling of air duct heater using the finite difference method
88%
Sarafraz M. , Peyghambarzadeh S. , Marahel A.
Polish Journal of Chemical Technology
|
2011
|
tom 13
|
nr 4
47-52
EN
In this research, mathematical modeling of a duct heater has been performed using energy conservation law, Stefan-Boltzman law in thermal radiation, Fourier's law in conduction heat transfer, and Newton's law of cooling in convection heat transfer. The duct was divided to some elements with equal length. Each element has been studied separately and air physical properties in each element have been used based on its temperature. The derived equations have been solved using the finite difference method and consequently air temperature, internal and external temperatures of the wall, internal and external convection heat transfer coefficients, and the quantity of heat transferred have been calculated in each element and effects of the variation of heat transfer parameters have been surveyed. The results of modelling presented in this paper can be used for the design and optimization of heat exchangers.
5
Content available remote Artificial neural network to predict the natural convection from vertical and inclined arrays of horizontal cylinders
88%
Amiri A. , Karami A. , Yousefi T. , Zanjani M.
Polish Journal of Chemical Technology
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2012
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tom 14
|
nr 4
46-52
EN
The main focus of the present study is to utilize the artificial neural network (ANN) in predicting the natural convection from horizontal isothermal cylinders arranged in vertical and inclined arrays. The effects of the vertical separation spacing to the cylinder diameter ratio (Py/d), horizontal separation spacing to the cylinder diameter ratio (Px/d) and Rayleigh number (Ra) variation on the average heat transfer from the arrays are considered via this prediction. The training data for optimizing the ANN structure is based on available experimental data. The Levenberg-Marquardt back propagation algorithm is used for ANN training. The proposed ANN is developed using MATLAB functions. For the best ANN structure obtained in this investigation, the mean relative errors of 0.027% and 0.482% were reached for the training and test data, respectively. The results show that the predicted values are very close to the experimental ones.
6
Content available remote Competitive adsorption of toxic metals on activated carbon
88%
Šváb M. , Sukdolová K. , Švábová M.
Open Chemistry
|
2011
|
tom 9
|
nr 3
437-445
EN
Competitive adsorption of zinc and copper on activated carbon is studied in this article. Main aim was to suggest an advanced model for competitive adsorption of both metals considering pH influence and precipitation. A surface-complexation approach was employed for the modeling. Two models were considered: simple adsorption and ion exchange. System “The Geochemists Workbench” was used for calculation of both static and dynamic adsorption tasks. From the batch experiments, concentration of four types of sorbing sites on the carbon surface and its protonation and sorption constants were deduced. Then, batch competitive adsorption experiments were compared with the models’ results. Finally, a column experiment (fixed bed adsorption) was carried out. It was observed that the model of ion exchange can satisfyingly predict both chromatographic effect and increase of zinc concentration in effluent over its initial value, although a quantitative agreement between the model and the experiment was not totally precise.
7
Content available remote Optimization methodology based on neural networks and genetic algorithms applied to electro-coagulation processes
88%
Piuleac C. , Curteanu S. , Rodrigo M. , Sáez C. , Fernández F.
Open Chemistry
|
2013
|
tom 11
|
nr 7
1213-1224
EN
An optimization methodology based on neural networks and genetic algorithms was developed and used to optimize a real world process - an electro-coagulation process involving three pollutants at different concentrations: kaolin (250–1000 mg L−1), Eriochrome Black T solutions (50–200 mg L−1), and oil/water emulsion (1500–4500 mg L−1). Feed-forward neural networks using heterogeneous combination of transfer functions were developed, leading to good results in the validation stage (relative error about 8%). The parameters of the process (concentration of pollutant, time, pH0, conductivity and current density) were optimized handling the genetic algorithm parameters, in order to obtain a maximum removal efficiency for each pollutant. Therefore, the optimization methodology combines neural networks as modeling tools with genetic algorithms as solving method. Validation of the optimization results using supplementary experimental data reveals errors under 11%. [...]
8
Content available Application of Index Models for Assessing Freshwater Microplastics Pollution
88%
Enyoh C. E. , Verla A. W. , Rakib M. R. J.
World News of Natural Sciences
|
2021
|
tom 38
37-48
EN
Due to the differences in reporting units and methodology on microplastics (MP) studies, there has been some difficulty in comparing results across studies. In this study, we presented index models that can be address this issue. Index models for pollution and health risks assessment was applied to MP data obtained from rivers in Nwangele L.G.A. Models such as microplastics contamination factor (MPCF), microplastics pollution load index (MPPLI), Microplastics polymer risk indices (Hi) and pollution risk index (MPR) for pollution and contamination assessment. Health risk models such estimated daily intake (EDI) and microplastic carcinogenic risks (MPCR) through oral and dermal pathway were also presented and applied. Results showed that there is no direct correlation of MP abundance with MPR. However, Hi correlated but with MPR. Increased MPs pollution risks and levels were extensively subject to the presence of harmful MPs polymers, just as the high MPs pollution loads index (MPPLI). The index models enabled easy comparison of MP pollution of the different rivers and provided concise information on the status of MPs in the rivers.
9
Content available remote Chemometrics as an option to assess clinical data from diabetes mellitus type 2 patients
88%
Nikolov M. , Simeonova P. , Simeonov V.
Open Medicine
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2009
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tom 4
|
nr 4
433-443
EN
The present study deals with the application of two major multivariate statistical approaches - Cluster Analysis (CA) and Principal Components Analysis (PCA) as an option for assessment of clinical data from diabetes mellitus type 2 patients. One hundred clinical cases of patients are considered as object of the statistical classification and modeling, each one of them characterized by 34 various clinical parameters. The goal of the study was to find patterns of similarity, both between the patients and the clinical tests. Each group of similarity is interpreted revealing at least five clusters of correlated parameters or five latent factors, which determine the data structure. Relevant explanation of the clustering is found based on the pattern of similarity like glucose level, anthropometric data, enzyme level, liver function, kidney function etc. It is assumed that this classification could be of help in optimizing the performance of clinical test for this type of patients and for designing a pattern for the role of the different groups of test in determining the metabolic syndrome of the patients.
10
Content available Mathematical model of a plate fin heat exchanger operating under solid oxide fuel cell working conditions
75%
Kupecki J. , Badyda K.
|
11
Content available Analiza oraz metodyka modelowania systemu produkcyjnego w przedsiębiorstwie wytwórczym branży stolarskiej
63%
Grzelak M.
Studia Ekonomiczne
|
2017
|
tom 337
46-60
PL
Funkcjonowanie firm produkcyjnych opiera się na wydajnym systemie produkcji składającym się z elementów wektora wejściowego (X), procesu transformacji i wektora wyjściowego (Y) wraz z zaakceptowaną koncepcją zarządzania. Celem artykułu jest przedstawienie metody modelowania wybranego systemu produkcji oraz szczegółowej analizy podstawowego procesu produkcyjnego w badanym przedsięwzięciu. Szczególną uwagę zwrócono na metodę obliczania programu produkcyjnego, skutecznego funduszu czasu pracy, taktu, zadania godzinowego, zapotrzebowania na materiały i surowce. Ponadto omówiono metody szacowania liczby maszyn i urządzeń produkcyjnych, urządzeń technologicznych, niezbędnych pracowników produkcji bezpośredniej, wymaganej powierzchni produkcyjnej i poziomu przechowywanych zapasów.
EN
Functioning of manufacturing companies is based on an efficient production system consisting of elements of the input vector (X), transformation process and output vector (Y) together with the accepted management concept. The aim of the article is to present the method of modeling the selected production system and detailed analysis of the basic manufacturing process in the examined enterprise. Particular attention has been paid to the calculation method of the production program, the effective working time fund, the tactic, the hourly task, the demand for materials and raw materials. In addition, the methods of estimating the number of machines and production equipment, technological equipment, necessary direct production staff, the required area of the company and the level of stocks kept are discussed.
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